Fluid pressure producing device



Filed Dec. 13, 1948 K R M m w W H Z mm 4 W. m e 4 a Z .@w n a m 8 M %Q4Q 5 9 4 "I. W 9 a W 4 V I! 8 A 6 4 4 8 0 6 7 Z 8 2 M HMS M 5 0 H 9 o 2 98 8 0 2 m a 6 3 3 w Patented June 1, 1954 FLUID PRESSURE PRGDUCINGDEVICE Harvey C. Swift, Birmingham, Mich, assignor to Bendix AviationCorporation, Detroit, Mich., a

corporation of Delaware Application December 13, 1948, Serial No. 64,951

2 Claims.

This invention relates to fluid pressure brake systems and in particularto fluid pressure producing devices for such systems.

Heretofore in the construction of fluid pressure producin devices havinga fluid reservoir, a cylinder supply therefrom, and a pistonreciprocable in the cylinder, the cylinder has generally been suppliedwith two ports providing communications between the cylinder and thereservoir. These ports are generally known in the art as a supply portand a compensating port. The latter is locked slightly in advance of asealing cup seated on the head of the piston, when the piston is in aretractile position. Hence, when the piston is moved on its compressionstroke the pressure created in the cylinder forces the wall of the cupinto the compensating port and this results in serious injury to thecup. The instant invention aims to overcome the objection.

An object of the invention is to provide a fluid pressure producingdevice having but one intake port adapted to function both as a supplyport and as a compensation port.

Another object of the invention is to provide a fluid pressure deviceincluding a reservoir, a cylinder supply therefrom, a piston movable inthe cylinder and means for filtering the fluid as it passes from thereservoir to the cylinder.

Yet another object of the invention is to provide a fluid pressuredevice including a cylinder having a section of its wall made of porousmaterial adapted to function as a supply port for the cylinder.

A further object of the invention is to provide a fluid pressure deviceincluding a reservoir, a cylinder supply therefrom having a section ofporous material adapted to function as an intake port and also as acompensating port for cylinder.

Other objects and advantages of the invention will appear from thefollowing description when taken in connection with the drawin forming apart of this specification, and in which;

Fig. l is a schematic View of a fluid pressure braking system embodyingthe invention, and

Fig. 2 is a vertical sectional view of the fluid pressure producingdevice of the system showing the piston of the device in retractedposition.

Referring to the drawing for more specific details of the invention asingle casting includes a reservoir it having a fillin opening l2normally closed as by a hollow plug M provided with apertures It forventing the reservoir to the atmosphere, and a shield I B depended fromthe plug inhibits fluid from splashing through the apertures.

A. cylinder 20 depended from the bottom of the reservoir has a doublediametral bore 22, the larger bore of the cylinder communicates directlywith the reservoir and at the juncture of the bores is an internalshoulder 24. The free end of the cylinder is closed as by a head 26, andthe head has diametrically disposed bosses 28 and 39 tapped to providedischarge ports 32 and as communicating with the smaller bore of thecylinder, and arranged at the juncture of the reservoir and the cylinderare parallel bosses 36 and 38 tapped for the reception of fasteningmeans, not shown.

A sleeve ll) extended upwardly from the bottom of the reservoir incoaxial relationship with the cylinder 20 has a bore 32 the diameter ofwhich is greater than the diameter of the larger bore of the cylinderand this dilferential in bores provides a shoulder 44 at the juncture ofthe bottom of the reservoir and the sleeve. Spaced inlet ports 55 arearranged in the wall of the sleeve at the base thereof and in free endof the sleeve is a shoulder 48.

A porous sleeve 50 preferably of sintered metal is fltted in the sleeve30. It completely covers the intake ports 45 and elfectively functionsas a filter. The sleeve has an inner diameter commensurate with thediameter of the bore 22 of the cylinder 20. One end of the sleeve 56seats on the shoulder 34, the other end thereof is aligned with theshoulder 48, and the sleeve is held against displacement by a washer 52seated on the shoulder 68 and the sleeve 56, and secured in place by aretaining rin 55 seated in a groove in the wall of the cylinder.

A piston 55 reciprocable in the bore of the cylinder and the poroussleeve 59 has a recessed head 55, and a reduced body portion 60providing in conjunction with the wall of the cylinder an annularchamber 62 communicating with the bore 22 of the cylinder by way ofports 64 in the head of the piston, and with the reservoir is by way ofthe inlet ports 56 and the porous sleeve 56, when the piston is in itsretracted position. The piston also has a skirt 66 supporting a sealingcup and an axially disposed socket 79 extended well into the body of thepiston.

A two-way valve 12 seated on the shoulder 24 in the cylinder 29 servesto control the flow of fluid and a spring 14 interposed between thevalve and the head of the piston serves to retain the valve on theshoulder, and to return the piston to its retracted position.

The reservoir ID has an opening 16 in the top thereof immediately abovethe sleeve 40, and a flange I8 spaced from the perimeter defining theopening provides in conjunction with the top of the reservoir a shoulder80.

A thrust pin 82 seated in the socket 19 of the piston has thereon acoupling 84. The thrust pin is embraced by a rubber diaphragm 86 securedon the shoulder 80 by a cup 88 fitted tightly in the sleeve 18. The cuphas an axial opening for the reception of the thrust pin and a flange 99on the cup 88 receives a flexible boot 92 connected to the coupling 84,and a rod 99 received by the coupling is pivotally connected to a footpedal lever 96 pivoted on a suitable support 98 and connected by aretractile spring I99 to a fixed support I02.

Fluid pressure delivery pipes I94 and I96 con nected to the dischargeports 32 and a l of the cylinder 20 have branches connected respectivelyto fluid pressure actuated motors I98 preferably arranged in pairs; onepair for the actuation of brakes associated with the front wheels of avahicle, and another pair for the actuation of brakes associated withthe rear wheels of the vehicle.

The brakes are each of conventional type including a fixed support orbacking plate HE], rotatable drum H2 associated therewith, a pair offriction elements or shoes H4 mounted on the backing plate and adaptedto be actuated by a motor corresponding to the motors I98 for movementinto engagement with the drum against the resistance of a retractilespring H6 connected between the shoes.

In operation, upon depressing the foot pedal lever 96 force istransmitted from the lever through the linkage 82 and 94 to the piston56, resulting in movement of the piston on its compression stroke.During an initial movement of the piston the sealing cups '68 covers theporous sleeve or member 50 thereby cutting off communication between thereservoir and the cylinder. Upon further movement of the piston on itscompression stroke fluid is expelled from the cylinder past the two-wayvalve 24 which inhibits retrograde movement of the fluid, and throughthe fluid pressure delivery pipe 109 and I99 and the branches thereofinto the fluid pressure actuated motors E98, causing actuation of themotors with the resulting movement of the shoes I I4 into engagementwith the drums H2 against the resistance of the retractile springs H6resulting in retarding the speed of the vehicle.

Upon release of the foot pedal lever 96 the lever is returned to itsnormal position under the influence of the retractile spring I90. As thefoot pedal lever moves to its retractile position the .thrust pin 82connected thereto is retracted.

This results in release of the piston 59 whereupon the spring 7 4becomes efiective to return the piston to its retracted position. Uponthe initial movement of the piston on its retracted position fluid isdrawn from the reservoir through the ports 46 and the cintered sleevemember 59 into the cylinder.

During this operation fluid is returned to the cylinder 20 from thefluid pressure actuated motor 688. Under the influence of the retractilesprings H5, and when the cylinder is filled, any fluid in excess of thequantity required to completely fill the cylinder is returned throughthe cintered sleeve or member 59 and the ports 48 to the reservoir. Itis to be observed that should any expansion or contraction of the fluidin the system take place due to change in temperature, such expansion orcontraction is readily compensated for by the flow of fluid through theports 8 in the head of the piston into the annular chamber 62 thencethrough the cintered sleeve member 50 and intake ports 46 to thereservoir. It is also to be observed that the fluid flowing from thereservoir to the cylinder is completely filtered and that the fluidreturning from the cylinder to the reservoir serves to cleanse thecintered material and/or filter.

Although this invention has been described in connection with certainspecific embodiments the principles involved are susceptible to numerousother applications that will readily occur to per sons skilled in theart. The invention is, therefore, to be limited only as indicated by thescope of the appended claims.

Having thus described the various features of the invention what I claimas new and desire to secure by Letters Patent, is:

1. In a fluid pressure producing device a reservoir, a cylinder dependedtherefrom, an annular flange on the bottom of the reservoir arrangedconcentrically to the cylinder and provided with spaced ports, a poroussleeve in the annular flange covering the ports and providing acontinuation between the reservoir and the cylinder, a pistonreciprocable in the cylinder and porous sleeve, means for moving thepiston on its compression stroke and means for returning the piston toits retracted position.

2. In a fluid pressure producing device a reservoir, a cylinder dependedtherefrom, a fluid pressure system connected to the cylinder, a poroussleeve supported in the reservoir coaxially with respect to the cylinderand providing in effect a continuation thereof and an inlet therefor, apiston reciprocable in the cylinder and sleeve, a sealing cup on thepiston adapted to uncover a substantial part of the porous sleeve whenthe piston is in its retracted position, means for moving the piston onits compression stroke and means for retracting the piston.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,175,447 Rike Oct. 10, 1939 2,245,991 Loweke June 17, 19412,294,351 White Aug. 25, 1942 2,358,887 Temple Sept. 26, 1944 2,373,745Conway Apr. 17, 1945 2,447,142 Smith et al Aug. 17, 1948

